CN-121970783-A - Preparation method and application of nanoemulsion bacteriostatic agent with mango peel as material

CN121970783ACN 121970783 ACN121970783 ACN 121970783ACN-121970783-A

Abstract

The invention discloses a preparation method and application of a nano emulsion bacteriostat using mango peel as a material, belonging to the technical field of plant source pesticide preparations; dissolving the extract with a second polar solvent, regulating pH to isoelectric point, performing ultrasonic-assisted extraction, standing for layering to obtain upper organic phase, removing solvent to obtain refined extract, mixing with emulsifying agent and water to form pre-emulsion, and performing high-speed shearing and high-pressure homogenization treatment to obtain the nanoemulsion antibacterial agent. The invention also provides application of the prepared nanoemulsion bacteriostat, solves the technical problems of low extraction efficiency, easiness in degradation, poor stability, difficulty in uniform dispersion and the like of the existing plant-source bacteriostat, and realizes efficient enrichment and stable encapsulation of active ingredients by integrating extraction, refining and nanoemulsion technologies, thereby remarkably improving the bacteriostasis effect and storage stability of the final product.

Inventors

YANG ZHENGZHOU
XIE XIAONA
KE QIN
PENG QINGQING
Muzamir Hussein
LANG TAO

Assignees

百色学院

Dates

Publication Date: 20260505
Application Date: 20260115

Claims (10)

1. The preparation method of the nanoemulsion bacteriostatic agent using mango peel as a material is characterized by comprising the following steps: S1, crushing and sieving a dried mango peel raw material to obtain mango peel powder, mixing the mango peel powder with a first polar solvent according to a proportion to form a first mixed solution, and carrying out heating reflux extraction on the first mixed solution to obtain a first extracting solution; S2, filtering the obtained first extract, separating solid residues to obtain a first filtrate, and performing reduced pressure distillation on the first filtrate to remove a first polar solvent to obtain a first crude extract; S3, mixing the obtained first crude extract with a second polar solvent, dissolving the first crude extract, wherein the polarity of the second polar solvent is lower than that of the first polar solvent, adding acid liquor into the dissolved solution to adjust the pH value of the mixed solution to an isoelectric point range, performing ultrasonic-assisted extraction, standing the extracted mixed solution, inducing the mixed solution to form an upper organic phase containing target antibacterial components and an aqueous phase containing impurities, and separating and obtaining the upper organic phase; S4, performing reduced pressure distillation on the obtained upper organic phase, removing the second polar solvent to obtain a refined mango peel extract, and mixing the refined mango peel extract, an emulsifying agent and distilled water according to a predetermined proportion to form a pre-emulsion mixture; s5, carrying out high-speed shearing and dispersing on the obtained pre-emulsion mixture, transferring the pre-emulsion mixture into a high-pressure homogenizer, and carrying out homogenization treatment under the set homogenization pressure and circulation times to finally obtain the nano-emulsion bacteriostat.
2. The method for preparing a nano emulsion bacteriostat using mango peel as material according to claim 1, wherein in step S1, when the dried mango peel raw material is crushed and sieved to obtain mango peel powder, controlling the particle size distribution of the sieved mango peel powder to make the particle size of the powder be within a predetermined particle size range, specifically 80-200 meshes; When the first polar solvent is ethanol and methanol aqueous solution with the volume concentration of 60% -90%, and the mango peel powder and the first polar solvent are mixed in proportion to form a first mixed solution, heating reflux extraction is carried out by adopting a step-by-step feeding and step heating program, part of the first polar solvent and all the mango peel powder are mixed at room temperature and stirred at a low speed for pre-soaking, then the rest of the first polar solvent is added, the first mixed solution is heated to a first heat preservation temperature at a first heating rate and kept for a preset heat preservation time, then the main reflux extraction is carried out by continuously heating to a second heat preservation temperature higher than the first heat preservation temperature at a second heating rate, the second heat preservation temperature is 70-90 ℃, the main reflux extraction time is 1-3 hours, and the whole heating reflux extraction process is carried out in an inert gas environment.
3. The method for preparing the nano emulsion bacteriostat using mango peel as a material according to claim 1, wherein in step S2, when the first filtrate is subjected to reduced pressure distillation, a reduced pressure distillation mode of program temperature control is adopted, and the method specifically comprises the following steps: Evaporating the main part of the first polar solvent under the first distillation temperature and the first vacuum degree, synchronously increasing the vacuum degree to a higher second vacuum degree when the volume of the distillate is reduced to a preset proportion of the initial volume, and correspondingly increasing the temperature to the second distillation temperature to continue distillation, recovering the distilled first polar solvent through a condenser in the whole distillation process, continuously stirring the first filtrate through a magnetic stirrer positioned at the bottom of the distillation flask, stopping heating and maintaining the vacuum degree when the condition that the materials in the distillation flask are changed into thick paste from flowing liquid is observed, and removing the residual first polar solvent by utilizing the system waste heat and continuous stirring to obtain the first crude extract.
4. The method for preparing a nano emulsion bacteriostat using mango peel as a material according to claim 1, wherein in the step S3, the second polar solvent is ethyl acetate, dichloromethane, n-hexane or a mixture thereof, when an acid liquor is added to adjust the pH value of the mixed solution, the acid liquor is an aqueous solution of at least one organic acid of citric acid, acetic acid or lactic acid, and the molar concentration of the acid liquor is pre-configured according to a preset value; in the process of adding acid liquor dropwise, dynamically controlling the dropping speed according to the dropping speed of the pH meter, slowing down the dropping speed when the pH value is close to the isoelectric point range, and assisting in slow magnetic stirring to promote the whole uniformity of the mixed solution, wherein the pH value of the isoelectric point range is between 3.5 and 5.0; After the pH adjustment is completed, the mixed solution is left to stand and observed for clarity, if new fine flocs appear, gentle stirring is restarted and a trace of acid solution is added until the flocs are completely dissolved and the pH is stabilized again within the isoelectric point range, followed by ultrasound-assisted extraction.
5. The method for preparing the nano emulsion bacteriostat using mango peel as a material according to claim 4, wherein in the step S3, after adding acid liquor to adjust the pH value of the mixed solution to an isoelectric point range, carrying out ultrasonic auxiliary extraction, carrying out ultrasonic treatment in an ice water bath container, directly inserting the mixed solution by using a probe type ultrasonic generator, setting the ultrasonic mode as pulse type, alternately carrying out pulse working time and pulse intermittent time, stopping controlling the temperature by the pulse intermittent time, enabling the mixed solution to be temporarily restored to be close to room temperature, and reducing the mixed solution to the set temperature of the ice water bath again by the pulse working time; In the extraction process, inert gas is continuously introduced to the surface of the mixed solution to remove oxygen, the mixed solution obtained by extraction is statically transferred to a constant temperature oscillator and oscillated at a slow rotation speed, the standing time is prolonged until the mixed solution is completely layered and the interface is clear, and the mixed solution after standing is separated by a separating funnel pre-wetted by a second polar solvent to obtain an upper organic phase so as to reduce the adsorption loss of the upper organic phase on the funnel wall.
6. The method for preparing the nano emulsion bacteriostat using mango peel as a material according to claim 1, wherein in the step S4, when the refined mango peel extract, the emulsifier and the distilled water are mixed according to a preset proportion, the refined mango peel extract and the emulsifier are uniformly mixed in a preheating container to form an oil phase mixture, meanwhile, the distilled water is heated to the same preset temperature as the oil phase mixture, the preset temperature is 50-70 ℃, then, the preheated distilled water is slowly added into the oil phase mixture in batches under the conditions of constant temperature and continuous stirring, the initial uniform viscous paste is formed by adding 30-50% of distilled water, and then all the residual distilled water is added and is switched to medium-speed stirring until a uniform pre-emulsion mixture is formed.
7. The method of claim 6, wherein when the refined mango peel extract is mixed with the emulsifier uniformly in the preheating container to form the oil phase mixture, the emulsifier is preheated to a temperature above the phase transition temperature of the emulsifier and kept in a liquid state, then the emulsifier and the refined mango peel extract are mixed in an inert gas environment, a thermostatic container with a wall scraping stirrer is adopted in the mixing process, the adding flow rate of distilled water is controlled by a metering pump in the process of slowly adding the preheated distilled water into the oil phase mixture, and when a part of distilled water is added for the first time, the distilled water is uniformly sprayed onto the surface of the continuously stirred oil phase mixture in the form of atomized spray, the diameter of sprayed liquid drops is controlled to be in a preset range, after the initially uniform viscous paste is formed, the mode of adding the residual distilled water is changed into a mode of injecting in a laminar flow through a small diameter conduit immersed under the liquid level of the paste, meanwhile, the stirring speed is gradually reduced from a high speed to a medium speed, the water temperature of the thermostatic container is kept constant until no visible uniform oil phase or water phase gathers in the pre-emulsion mixture, and the pre-emulsion is formed.
8. The method for preparing the nano emulsion bacteriostat using mango peel as material according to claim 1, wherein in step S5, when the pre-emulsion mixture is subjected to high-speed shearing and dispersion and then transferred to a high-pressure homogenizer for homogenization treatment, a segmented stepped homogenization pressure program is adopted for treatment, and the method specifically comprises the following steps: Homogenizing the material for the first cycle times under the initial homogenizing pressure, then stepwise raising the homogenizing pressure to a higher target homogenizing pressure, homogenizing the rest cycle times under the target homogenizing pressure, wherein the initial homogenizing pressure is 30-60MPa, the target homogenizing pressure is 100-150MPa, the total cycle times are 6-10 times, the whole homogenizing treatment process is carried out in a high-pressure homogenizer with an external circulating cooling jacket, the temperature of the material at a discharge port of the homogenizer is controlled to be lower than a preset temperature, and after the last homogenizing cycle is completed, the obtained nano emulsion bacteriostatic agent is immediately transferred into a sealed container which is precooled to the same temperature range for collection and preservation.
9. The method for preparing a nano emulsion bacteriostatic agent using mango skin as material according to claim 8, wherein in the process of stepwise increasing the homogenizing pressure from the initial homogenizing pressure to the target homogenizing pressure, a continuously adjustable pressure control system is adopted to enable the pressure to be increased linearly from the initial homogenizing pressure to the target homogenizing pressure at a preset gentle rate, during the linear increase of the pressure, the high-pressure homogenizer keeps a homogenizing treatment state, but the opening of a homogenizing valve is adjusted synchronously and finely according to the pressure increase to maintain a stable shearing rate; when the pressure reaches the target homogenizing pressure, the pressure is kept for stable homogenization for a predetermined period of time, then the homogenization treatment of the residual circulation times is carried out, after all the homogenization circulation is completed, the nano emulsion bacteriostat is transferred into the pre-cooling closed container, the flow rate of the transfer pipeline is controlled to be below a speed limit value through the flow valve so as to avoid the shearing force to destroy the emulsion structure again, and the pre-cooling closed container keeps the negative pressure in the transfer process.
10. The nanoemulsion bacteriostat obtained by the preparation method according to any one of claims 1-9 and application of the nanoemulsion bacteriostat as a crop protection product prepared by taking the nanoemulsion bacteriostat as a constituent component.

Description

Preparation method and application of nanoemulsion bacteriostatic agent with mango peel as material Technical Field The invention relates to the technical field of botanical pesticide preparations, in particular to a preparation method and application of a nanoemulsion bacteriostatic agent taking mango peel as a material. Background In agricultural production, prevention and control of crop diseases are key links for guaranteeing yield and quality. For a long time, chemical synthesis pesticides are widely used due to the characteristics of high efficiency and quick acting, but the problems of pesticide residue, enhanced pathogen resistance, environmental pressure and the like brought by the chemical synthesis pesticides are increasingly prominent. Therefore, the development of efficient, low-toxicity and environment-friendly green alternative pesticide products is an important research direction for the sustainable development of agriculture at present. The plant pesticide is developed by utilizing natural antibacterial active substances contained in plants, and has been widely focused because of the potential advantages of renewable resources, easy degradation, various action mechanisms, difficult resistance induction and the like. Mango peel is often discarded or only used with low value as a large amount of by-product from the mango processing industry. Researches show that the mango peel contains abundant secondary metabolites such as polyphenol, flavone and the like, and the ingredients have obvious antioxidant and antibacterial activities. Therefore, the mango peel is developed into a plant-source bacteriostat, so that a new material source can be provided for crop protection, the high-value utilization of agricultural wastes can be realized, and the economic and environmental benefits are achieved. However, the conversion of the active ingredient in mango peel into a practically usable agricultural bacteriostatic product still faces a series of technical challenges. First, it is not easy to extract the target antibacterial ingredient from the mango peel with high efficiency and selectivity. Traditional extraction methods (such as simple extraction, water decoction and the like) tend to have limited extraction efficiency, and the obtained extract has complex components and contains a large amount of sugar, protein, pigment and other impurities, so that the content of target active ingredients is relatively low, and the efficacy of subsequent preparations is directly influenced. Secondly, the active ingredients in the plant extract, especially the polyphenols, have the problem of unstable chemical properties, and are easy to undergo oxidation, polymerization and other reactions to inactivate in the presence of light, heat or oxygen, which brings serious test to the shelf life of the product and the lasting period of the field application. More critical is how to effectively disperse the hydrophobic plant extract in the application medium based on water, and make it stably exist and uniformly cover the surface of crops, which is a core problem in the preparation process. Conventional dosage forms, such as wettable powder, emulsifiable concentrates or common emulsions, are often difficult to realize uniform dispersion and stable suspension of active ingredients, and are easy to cause the phenomena of precipitation, layering or oil phase precipitation and the like. This not only affects the uniformity of the application, resulting in poor control, but also may clog the spray head, causing inconvenience to the application. In addition, larger particle or droplet sizes reduce the effective contact area of the agent with the target pathogen, potentially limiting its full play of biological activity. In the prior art, some studies have been attempted to modify the formulation of plant extracts, for example, to prepare microemulsions or ordinary emulsions. These methods improve dispersibility to some extent, but may still suffer from insufficient physical stability for a long period of time, slow degradation of the active ingredient during storage, or the need for large amounts of organic solvents and surfactants. In particular, how to solve the problems of multiple links such as extraction, purification, protection, high-efficiency delivery and the like of active ingredients by a set of systematic process from the beginning of raw material treatment, so that a mango peel source bacteriostatic agent product with high activity, high stability and easy use is finally obtained, the existing technical scheme is not perfect, and further improvement and innovation are still needed. Disclosure of Invention The invention solves the technical problems of low extraction efficiency, easy degradation, poor stability, difficult uniform dispersion and the like of the active ingredients of the existing plant source bacteriostat, provides a preparation method and application of the nanoemulsion bacteriostat which takes mango